The Troodontidae

Smartest of the non-avian dinosaurs?

The Troodontidae are a small group (maybe five different species) of very rare and hence
poorly known maniraptorans. They are only known from a few incomplete specimens
from the Cretaceous
period of North America and Mongolia, so their exact affinities to other maniraptorans
are uncertain. It has been suggested that they were the ancestors of birds, but this is not
accepted; a
dromaeosaur is currently thought to be the ancestor of all birds. Even though
dromaeosaur and troodontids are outwardly similar, scientists are not certain yet that they
are closely related, but are confident that troodontids lie within the clade Maniraptora.

Troodontids are best exemplified by the genera Saurornithoides (from western
Mongolia), Troodon (from North America), and Sinornithoides. They were
small (about the size of a small adult human), with long and slender hind limbs useful for
rapid locomotion, and a long skull filled with distinctive recurved and saw-edged teeth (see
the picture of two troodontid teeth from the UCMP collections).
Troodontid manus (hands  manus is spelled the same for the singular and plural) were
large and flexible, capable of precise grasping movements. The
pedes (feet) bore an enlarged claw similar to those of the Dromaeosauridae, but not as
large, and probably not used in predation.

The most interesting feature of troodontids is their skull  the brain case is the largest
relative to body size of all non-avian dinosaurs, the orbits (eye openings in the skull) are
very large, and the brain cavity suggests well developed centers for sight and hearing. Were
troodontids the smartest dinosaurs of their time? Maybe, but measuring intelligence even
on living animals is an imprecise matter in its own right; measuring the
intelligence of extinct animals from fragmentary bones is mostly fantasy, but probably
close to the truth. Troodontids, judging from their cranial anatomy and
cursorial adaptations, were
likely agile, fast carnivores with acute senses. Like all other non-avian dinosaurs, however,
they vanished at the end of the
Mesozoic era.